U.S. Naval Research Laboratory, Washington, DC, USA.
American Society for Engineering Education, Washington, DC, USA.
Sci Rep. 2016 Sep 13;6:32959. doi: 10.1038/srep32959.
Polar dielectrics have garnered much attention as an alternative to plasmonic metals in the mid- to long-wave infrared spectral regime due to their low optical losses. As such, nanoscale resonators composed of these materials demonstrate figures of merit beyond those achievable in plasmonic equivalents. However, until now, only low-order, phonon-mediated, localized polariton resonances, known as surface phonon polaritons (SPhPs), have been observed in polar dielectric optical resonators. In the present work, we investigate the excitation of 16 distinct high-order, multipolar, localized surface phonon polariton resonances that are optically excited in rectangular pillars etched into a semi-insulating silicon carbide substrate. By elongating a single pillar axis we are able to significantly modify the far- and near-field properties of localized SPhP resonances, opening the door to realizing narrow-band infrared sources with tailored radiation patterns. Such control of the near-field behavior of resonances can also impact surface enhanced infrared optical sensing, which is mediated by polarization selection rules, as well as the morphology and strength of resonator hot spots. Furthermore, through the careful choice of polar dielectric material, these results can also serve as the guiding principles for the generalized design of optical devices that operate from the mid- to far-infrared.
由于具有较低的光学损耗，极性介电材料在中长波红外光谱范围内作为等离子体金属的替代品受到了广泛关注。因此，由这些材料组成的纳米级谐振器在品质因数方面超越了等离子体等效物所能达到的水平。然而，直到现在，在极性介电光学谐振器中仅观察到了低阶、声子介导的局域极化激元共振，即表面声子极化激元（SPhP）。在本工作中，我们研究了在半绝缘碳化硅衬底上刻蚀的矩形柱中激发的 16 种不同的高阶、多极、局域表面声子极化激元共振。通过拉长单个支柱轴，我们能够显著改变局域 SPhP 共振的远场和近场特性，为实现具有定制辐射模式的窄带红外光源开辟了道路。这种对共振近场行为的控制还可以影响通过偏振选择规则以及谐振器热点的形态和强度来介导的表面增强红外光学传感。此外，通过仔细选择极性介电材料，这些结果还可以作为从中波到远红外操作的光学器件的一般设计的指导原则。
